The invention relates to a filling apparatus for presses and a method for operating such a press. More particularly, the invention relates to a filling apparatus for axial powder presses.
For filling a powder press with powder, especially ceramic powder and iron powder, a filling device is moved between each pressing operation over an opening in a filler plate, or over an opening in a die plate embedded in the filler plate of a die set, to fill the opening with powder. Prior to compacting the powder, the filling device is withdrawn to a rest position next to the press. For moving the filling device, there are different known actuating mechanisms, such as crank or spindle mechanisms, which are driven, for example, hydraulically or electromechanically, as well as hydraulic cylinders or servomotors.
The filling apparatus comprises a filling shoe firmly mounted on a filler main body of a filler drive and configured to move forward and backward together with it on the filler plate. Into a centrally arranged opening of the filling shoe there is introduced a filling tube which is rigidly connected to the filling shoe and to the filler drive. At the end of the filling tube projecting out from the filling shoe there is fixed a hose through which powder is fed from a hopper. The hopper is normally arranged above the filling apparatus and laterally at the press.
For filling the die with powder, the filling shoe must be moved over the opening in the die plate and be pressed firmly against it in order to be able to ensure safe, uniform and adequate filling of the die. The contact pressure must be sufficiently high to prevent powder from entering between the filling shoe and the filler plate. The required pressure must be particularly high, if, during displacement of the filling apparatus, the hose, which is normally partly filled with heavy powder, and the hopper are swiveled together with the filling apparatus and exert in particular on the filling shoe a force acting in opposite direction to the displacement and tilting the filling shoe.
For pressing the filling shoe against the filler plate, two methods are commonly used. According to the first method, the filler drive, together with the filling shoe is pressed at an angle from above onto the filler plate or die plate, whereby the total own weight of the filling apparatus rests on the filling shoe and at the same time has a negative effect on guidance in that it acts tilting like a lever. In another method the whole filler drive with the filling shoe is mounted for a swiveling movement around a mounting axis arranged outside the whole apparatus.
It is a disadvantage that onto the filler plate and onto the die and through the latter onto the die set of the press there acts a non-centric pressure at an angle from above or a tensile force at an angle from below which can lead to malfunction, wear and faulty pressing. In addition the apparatuses are of complex structure, difficult to adjust, and have to be replaced more or less completely at regular intervals because the filling shoe is often made of plastic and wears quickly as it is pulled over the filler plate, especially if, due to tilting, remnants of powder enter between the filling shoe and the filler plate.
An object of the invention is to propose a filling apparatus, especially for axial powder presses, which has a simple structure and allows uniform contact pressure of the filling shoe onto the filler plate and/or die plate.
This object is solved by a filling apparatus having a filling device comprising a filler main body, a filling shoe arranged on the side of the press, and a powder feeding device. The filling device can be moved forward and backward on or above a filler plate and the filling shoe can be pressed in at least one filling position against the filler plate or a die embedded therein. The filling shoe is coupled to the filler main body of the filling device.
As a result of uncoupling, i.e., the separable adjustable coupling of the filling shoe to the filler drive plate, the filling shoe can be pressed against the filler plate with a uniform distribution of pressure. In addition, a pressure force may be adjustable and may be dosed accurately, wherein the weight of the whole filling apparatus no longer rests on the filler plate. This structure is also designed to avoid that the filling shoe rests on the filler plate in a tilted position. Furthermore, it is possible to replace the filling shoe individually and without much expenditure for installation work.
Advantageous configurations are the subject matter of dependent claims.
Coupling of the filling shoe to the filler drive plate via a frame permits the filling shoe to be pressed against the filler plate with good possibility of control. Forces acting, for example, from the filling hose onto the filling apparatus as the latter is being pushed, will no longer be transferred onto the filling shoe.
Coupling the filling shoe via filling shoe mounting bolts being encompassed by recesses in the bottom of the frame, permits the filling shoe to be pushed in a simple and safe manner across the upper surface of the filler plate even in case of interrupted contact pressure.
While the filling shoe is pushed via the frame, a contact pressure adjustable to a lower value may act on the filling shoe ensuring that the filling shoe is pressed firmly enough against the filler plate to prevent remnants of powder from entering between the filling shoe and the filler plate.
Furthermore, the filling shoe, being a wearing part made of plastic in the majority of cases and, therefore, having to be replaced several times when producing large quantities of green parts or compact discs, can be removed and replaced quickly by simply lifting the frame from the filling apparatus.
Another aspect of the invention involves a filling apparatus having a filling device comprising a filler main body and a powder feeding device. The powder feeding device is adjustably and positionably coupled to the filler main body.
Due to the fact that the powder feeding device is mounted to the filler drive plate and not to the filling shoe, the load and the restoring forces of the filling hose, which in addition is filled with heavy powder or remaining quantities of powder, and of the powder feeding hopper, which can be swiveled over a certain angle, are no longer transmitted directly onto the filling shoe but onto the filler drive plate. There is no tilting of the filling shoe, thus avoiding among other things also loss of powder.
Fixing the powder feeding device to the filler drive plate by adjustable carriers permits variable adjustment of the outlet opening of the filling tubes above the die. With this structure, the density of the filled powder, in particular iron or ceramic powder, can be adjusted in a simple way not only in the die as a whole but also in individual portions of it. In this way, dies for producing eccentric sintered parts, e.g., for connecting rods, can be filled with powder more individually.
In particular, a complete plant can be quickly adapted to different compact discs. On the one hand a suitable filling shoe can be inserted into the filling apparatus without much work involved, on the other hand support of the filling tubes on the adjustable carriers permits simple and quick adjustment and fine adjustment of the outlet openings of the filling tubes.
Filling tubes with differentxe2x80x94even non-circularxe2x80x94cross sections, make it possible to feed powder or quantities of powder individually to certain areas of the die. By using adjustable flaps in the tubes, this filling effect can be adapted to specific requirements. This, together with the use of more than one filling tube arranged next to each other, permits optimized filling of the die. Therefore, filling pressure and density in particular are individually adjustable.
Generally speaking, adjustment of the individual assemblies is easier because the individual adjusting elements are arranged for easy access in front of the press in the area of the filler drive plate.